Name____________________________________________period_________AP chemistry
Unit 1 worksheet
Read chapters 3.5-3.7, 4.1-4.4 and pg. 78: the mass spectrometer
1.
Calculate the percentage by mass of oxygen in the following compounds
b. Cr(NO 3 ) 3
a. NO 2
70%
61%
2.
Determine the empirical formula for each
a. 0.104 mol K, 0.052 mol C, and 0.156 mol O
b. 87.5 % N, 12.5% H NH 2
3.
What is the molecular formula of each of the following compounds?
a. Empirical formula, CH 2 , molar mass = 84 g/mol C 6 H 12
b. Empirical formula, NH 2 Cl, molar mass = 51.5 g/mol NH 2 Cl
4.
Determine the empirical and molecular formula
a. Ibuprofen contains 75.69% C, 8.80% H, and 15.51% O; molar mass about 206 g C 13 H 18 O 2
b. Adrenaline contains 59.0% C, 7.1% H, 26.2% O, and 7.7% N; MW about 180 amu C 9 H 13 O 3 N
5.
Quinone, an oxygenated hydrocarbon, is a chemical used in the photography industry. When a 0.144 g sample is analyzed
by combustion analysis, 0.352 g of carbon dioxide and 0.0480 g of water is produced. Find the empirical formula for
quinone.
C3H2O
6.
If an oxygen stream is not sufficient during a combustion analysis, the sample will undergo incomplete combustion,
meaning not all of the carbon atoms are fully oxidized to CO2 and other compounds, such as acetaldehyde and carbon
monoxide, are produced. Assuming these substances are not absorbed during combustion analysis, describe the errors that
would occur in determining the empirical formula if insufficient oxygen is used.
The calculated empirical formula would have too few carbon atoms and too many oxygen atoms
7.
Write a balanced net ionic reaction for each of the following.
a. Lithium metal is burned in air
4Li + O 2  2Li 2 O
b. Aluminum metal is added to a solution of copper (II) chloride
2Al + 3CuCl 2  2AlCl 3 + 3Cu
2+
3+
2Al + 3Cu  2Al + 3Cu
c. Manganese (II) nitrate solution is mixed with sodium hydroxide solution
Mn(NO 3 ) 2 + 2NaOH  2NaNO 3 + Mn(OH) 2
2+
Mn + 2OH  Mn(OH) 2
d. The hydrocarbon hexane, C 6 H 14 , is burned in excess oxygen
2C 6 H 14 + 19O 2  12 CO 2 + 14H 2 O
e.
f.
g.
h.
K 2 CO 3
Silver nitrate solution is added to potassium chromate solution
2AgNO 3 + K 2 CrO 4  Ag 2 CrO 4 + 2KNO 3
2+
2Ag + CrO 4  Ag 2 CrO 4
Hydrogen peroxide decomposes
H 2 O 2  2H 2 O + O 2
Solid calcium carbonate is reacted with sulfuric acid
CaCO 3 + H 2 SO 4  CaSO 4 + H 2 O + CO 2
2+
CaCO 3 + 2H+  Ca + H 2 O + CO 2
Ammonium sulfate solution and potassium hydroxide solution are mixed together
(NH 4 ) 2 SO 4 + 2KOH  K 2 SO 4 + 2NH 3 + 2H 2 O
+
i.
j.
k.
l.
-
2NH 4 + 2OH  2NH 3 + 2H 2 O
Strontium hydroxide is mixed with hydrofluoric acid
Sr(OH) 2 + 2HF  2H 2 O + SrF 2
2OH + 2HF  2H 2 O + 2F
Powdered strontium oxide is added to distilled water
SrO + H 2 O  Sr(OH )2
2+
SrO + H 2 O  Sr + 2OH
Chlorine gas is bubbled through a solution of potassium bromide
Cl 2 +2 KBr 2KCl + Br 2
Cl 2 + 2Br  2Cl + B r2
Potassium sulfide is reacted with nitric acid
K 2 S + 2HNO 3  2KNO 3 + H 2 S
2+
S + 2H  H 2 S
m. Solid lithium is added to distilled water
2Li + 2H 2 O  LiOH + H 2
+
2Li + 2H 2 O  2Li + 2OH + H 2
8.
When methyl alcohol, CH 3 OH is dissolved in water, a nonconducting solution results. When acetic acid dissolves in water,
the solution is weakly conducting. Describe what happens upon dissolution in the two cases, and account for the different
results.
Methyl alcohol does not dissociate or ionize. There are no ions moving around. Acetic acid is a weak acid is it partially
ionizes and a small amount of ions move around and conduct electricity.
9.
Show how the following dissociates or ionizes upon dissolving in water
a. Zinc chloride
b. nitric acid
c. iron (II) sulfate
d. ammonium carbonate
2+
a. ZnCl 2  Zn + 2Cl
+
b. HNO 3  H + NO 3
22+
c. FeSO 4  Fe + SO 4
+
2d. (NH 4 ) 2 CO 3  2NH 4 + CO 3
10. Formic acid, HCHO 2 , is a weak electrolyte. What solute particles are present in an aqueous solution of this compound?
+
(draw a picture of it in water) HCHO 2 , H , CHO 2
11. Will precipitation occur when the following are mixed? If so, name the precipitate
b. NaOH and K 2 SO 4
c. FeSO 4 and Pb(NO 3 ) 2
a. Na 2 CO 3 and AgNO 3
no precipitate
lead sulfate
Ag 2 CO 3
12. What are the spectator ions when the following react
a. Pb(NO 3 ) 2 + Na 2 SO 4
Sodium and nitrate
b. CuBr 2 + NaOH
Sodium and bromide
c. AgNO 3 + KI
Potassium, nitrate
13. Separate samples of a solution of an unknown ionic compound are treated with dilute AgNO 3 , Pb(NO 3 ) 2 and BaCl 2 .
2Precipitates form in all three cases. Which of the following anions could be the anion of the unknown salt? Br , CO 3 , NO 3
Carbonate
14. What is the difference between
a. A monoprotic acid and a diprotic acid
Donates one proton; donates two protons
b. A weak acid and a strong acid
Partially ionizes; completely ionizes
c. An acid and a base
Has Hydrogen; has hydroxide
15. Label as a strong, weak, or nonelectrolyte
d. HF
e. NaOH f. Mg(OH) 2
g. C 2 H 5 OH
a. HCl
b. NaF
c. CO 2
Strong
strong
non
weak
strong
weak
non
16. Classify each as a strong or weak acid or base
b. HClO 2 c. LiOH
d. NH 3
e. H 2 S
f. Al(OH) 3
a. HClO 4
Strong acid
weak acid
strong base
weak base
weak acid
weak base
17. The formation of glucose, C 6 H 12 O 6 produces ethyl alcohol, C 2 H 5 OH and CO 2 :
C 6 H 12 O 6  2C 2 H 5 OH + 2CO 2
a. How many moles of carbon dioxide are produced when 0.300 mol of glucose reacts?
0.600 mol
b. How many grams of glucose are needed to form 2.00 g of methyl alcohol?
3.91 g
c. How many grams of carbon dioxide form when 2.00 g of methyl alcohol are produced?
1.91 g
18. Aluminum sulfide reacts with water to form aluminum hydroxide and hydrogen sulfide.
a. Write the balanced equation for this reaction.
Al 2 S 3 + 6H 2 O  2Al(OH) 3 +3 H 2 S
b. How many grams of aluminum hydroxide are formed from 10.5 g of aluminum sulfide?
10.9 g
c. What is the percent yield if the mass obtained of aluminum hydroxide was 3.4 g?
32%
19. Automotive air bags inflate when sodium azide, NaN 3 , rapidly decomposes.
2NaN 3 (s)  2 Na (s) + 3 N 2 (g)
a. How many moles of nitrogen gas are produced by the decomposition of 1.50 moles of sodium azide?
2.25 mol
b. How many grams of NaN 3 are required to form 5.00 g of nitrogen gas?
7.74 g
3
c. How many grams of NaN 3 are required to produce 10.0 ft of nitrogen gas if the gas has a density of 1.25 g/L?
548 g
20. Why are the amounts of the product formed in a reaction determined only by the amount of limiting reaction?
The limiting reactant regulates the amount of products because it is completely used up during the reaction; no more
products can be made when one reactant is unavailable.
21. The fizz produced when an alka-seltzer tablet is dissolved in water is due to the reaction between sodium bicarbonate and
citric acid, H 3 C 6 H 5 O 7
3NaHCO 3 + H 3 C 6 H 5 O 7  3 CO 2 + 3 H 2 O + Na 3 C 6 H 5 O 7
In a certain experiment 1.00 g of sodium bicarbonate and 1.00 g of citric acid are allowed to react.
a. Which reactant is the limiting reactant?
NaHCO 3
b.
How many grams of carbon dioxide form?
0.524 g
c.
How much of the excess reactant remains after the limiting reactant is completely consumed?
0.238 g
22. Solutions of sodium carbonate and silver nitrate react to form solid silver carbonate and sodium nitrate. A solution
containing 5.00 g of sodium carbonate is mixed with one containing 5.00 g of silver nitrate. After the reaction is complete,
the solutions are evaporated to dryness, leaving a mixture of salts. How many grams of sodium carbonate, silver nitrate,
silver carbonate, and sodium nitrate are present after the reaction is complete? 3.46 g of sodium carbonate, 0 g of silver
nitrate, 4.00 g of silver carbonate, and 2.47 g sodium nitrate
23. A student is assigned the task of determining the mass percent of silver in an alloy of copper and silver by dissolving a
sample of the alloy in excess nitric acid and then precipitating the silver as AgCl. The the student pours 25 mL of the HNO 3
into a beaker and adds a 0.6489 g sample of the alloy. After the sample completely reacts with the acid, some saturated
NaCl(aq) is added to the beaker, resulting in the formation of an AgCl precipitate. Additional NaCl(aq) is added until no
more precipitate is observed to form. The precipitate is filtered, dried, and weighed to constant mass in a filter crucible.
The data are shown in the table below.
Mass of sample of copper - silver alloy
Mass of dry filter crucible
st
Mass of filter crucible and precipitate (1 weighing)
nd
Mass of filter crucible and precipitate (2 weighing)
rd
Mass of filter crucible and precipitate (3 weighing)
0.6489 g
28.7210 g
29.3587 g
29.2599 g
29.2598 g
a.)Calculate the number of moles of AgCl precipitate collected.
mass of AgCl collected = (29.2598 – 28.7210) g = 0.5388 g
−3
= 3.759 × 10 mol AgCl
b.)
Calculate the mass percent of silver in the alloy of copper and silver.
0.4055 g Ag
62.49% Ag
Review
24. What is the molar mass of cholesterol if 0.00105 mol weighs 0.406 g?
386.6 g/mol
25. After doing a calculation the display shows the number 3760.289 on the calculator. If the answer is supposed to have three
significant figures, the correct way to display the answer would be:
2
.
1
3
b 3760.
c. 376
d. 376 x 10
e. 3.76 x 10
a. 3.76 x 10
26. A solid sample of a metal is submerged in a large graduated cylinder. The water level in the graduate was 55.25 mL and the
final level was 61.00 mL. If the mass of the object was determined to be 23.795 g, what is the density of the metal?
3
3
3
c. 4.13 g/cm
d. 4.1 g/cm
e. 4.138 g/mL
a. 4 g/mL
b. 4.14 g/cm
27. Fill in the gaps
39
K
19
20
19
39
55
112
25
48
56
82
30
64
81
125
25
48
56
82
55
112
137
207
Mn
Cd
28. What are basic properties of metals, metalloids, and nonmetals?
Metals are conductors, malleable, shiny luster
Metalloids- semiconductors
Nonmetals- nonconductors
137
Ba
207
Pb
29. Determine the name of the group each belong to
a. Potassium
b. chlorine
Alkali metal
halogen
c. neon
noble gas
d. magnesium
alkaline earth metal
e. gold
transition metal
24
30. If you have 50.0 g of Copper and 300. g of Nickel, how many total atoms do you have? 3.55 x10 atoms
24
31. It was found that 7.0 x 10 atoms of an unknown element had a mass of 46.5 g. Identify the element and explain how you
know. He (the molar mas is 4)
32. Which of the following nuclei has 3 more neutrons than protons?
11
37
24
70
B
b. Cl
c. Mg
d. Ga
a.
33. The percentage abundance of the stable isotopes of chromium are:
50
52
53
54
24 Cr – 4.3%; 24 Cr – 83.8%; 24 Cr – 9.6%; 24 Cr – 2.4%.
(a) Sketch the mass spectrum that would be obtained from naturally occurring chromium. Check in class
(b) Calculate the relative atomic mass of chromium, correct to three significant figures. 52.1 amu
34. Is the spectrum to the right the mass spectrum of potassium or calcium? Justify your reasoning.
The mass spectrum must be for potassium. The average atomic mass for potassium is 39.098 while that of calcium
is 40.078. Since the largest peak is at a mass of 39, it follows that the average atomic mass will be near 39 amu.
The peak at mass number 40 is very small, so it is mathematically impossible to have an average around 40.